The conventional method of heating the passenger compartment of motor vehicles propelled by liquid cooled internal combustion engines relies on the passage of air through a heater core to which heat is supplied via the engine coolant. From a cold start, heater discharge air reaches 100.degree. F. (approximately 38.degree. C.) after six-eight minutes operation.
In the November 1968 issue of Mechanical Engineering, pages 48 to 53, inclusive, K. Thomas Feldman, Jr. and Glen H. Whiting, in an article entitled "Applications of the Heat Pipe", described a heat pipe as follows:
"The basic elements of the heat pipe are a closed outer shell, a porous capillary wick, and a working fluid."
The operation of a heat pipe is described as follows:
"Heating one region of the heat pipe evaporates working fluid and drives the vapor to other regions where it condenses, giving up its latent heat. In the wick, surface tension forces return the condensate back to the evaporator region through capillary channels."
The authors suggest that "a flexible heat pipe could connect the hot exhaust manifold of an automobile engine to heat rejection fins inside the car, thus providing a rapid startup near isothermal auto heating system which requires no water circulation pumps." Although this suggestion was made in 1968, to our knowledge the use of a heat pipe in an automobile heating system has not found acceptance. This may have been because of the difficulty of providing a suitable coupling of the heat pipe to the engine exhaust manifold or to the difficulty of packaging a heat pipe structure and related tubing in the engine compartment due to a lack of space.
The current use of catalytic converters in vehicle exhaust systems for exhaust gas emissions control has resulted in exhaust gas temperatures that are high enough during engine warmup to supply heat to a vehicle passenger compartment in one-third the time of a conventional system utilizing engine coolant as the source of heat.
It is, therefore, an object of the present invention to utilize a heat pipe to transfer exhaust heat passing through a heat exchanger located in a vehicle engine exhaust system that includes one or more catalytic converters.